Armature bends object but makes one side bump out
It looks like a Weight Paint issue. Sometimes weights can be applied accidentally and even a .01 influence will affect the mesh. There are two ways to check for that.

A) In Edit mode, scroll down the Properties panel on the 3D window (right panel, press N if hidden). Click on the vertices where the bump is and you will see a section called Vertex Weights". There you can see what bones are affecting the selected vertex. Press X to remove unwanted influences and fix the remaining weights.

B) In Weight Paint mode, go to the Options tab, find "Show Zero Weights" and press the Active button. The blue mesh now turns black and you are able to see if bones have an influence of less than .1. Use the Subtract brush to paint them out and then go to Tools>Weight Tools>Clean